Malleable Cast Iron Property

Malleable Cast Iron is the traditional material for manufacturing pipe fittings whose characteristics make it as ideal choice. It is an iron-carbon alloy which combines the outstanding properties of cast iron and steel to produce a material which can still be cast but has improved strength and ductility. It also allows the production of complex shapes combined with a thin wall section.

In its cast state it is very hard and brittle and unsuitable for most engineering applications. A controlled heat treatment process (annealing) is applied to the cast material which changes the structure and reduces the carbon content. The resulting microstructure gives a material which is less hard, no longer brittle and now has good malleable and ductile properties while retaining a sufficiently high strength.

Malleable Iron Metallography-Blackheart structure 70X –uniform carbon distribution

There are two distinct types of malleable cast iron which are dependent mainly on the annealing method used. Their names result from the different visual appearances at the fracture surfaces: Whiteheart malleable iron and Blackheart malleable iron.

Blackheart malleable iron is usually annealed in an inert atmosphere (protective gas or vacuum) and has a uniform microstructure. The higher carbon content is everly distributed throughout the structure.

 Material grade and properties:

Within the material types, a number of different grades are possible. The grades are defined by:

ü     Material type: blackheart and whiteheart

ü     Minimum tensile strength (MPa)

ü     Percentage elongation of a standard test piece.

Materials compare: